CICEET Progress Report for the period 9/01/01 through 3/01/02

Project Title: In-situ Treatment of PCBs in Marine and Freshwater Sediments using Colloidal Zero-Valent Iron
Principal Investigator(s): Kevin H.Gardner, Ph.D., P.E.

Accomplishments
Scheduled Tasks:
There is an urgent national need for in-situ sediment remediation methods to be developed that can cost-effectively treat large volumes of contamination in a timely manner. The overall goal of this research is to develop a robust technology to dechlorinate polychlorinated biphenyls (PCBs) in marine and fresh-water sediments using colloidal zero-valent-iron (ZVI).

Specific objectives include:

1. organizing a set of batch experiments to be performed during the first year of the project to determine the minimum mass of ZVI required for treatment, the influence of temperature on reaction kinetics, the possibility of using different size iron particles, the affects of microbial activity on the system.
2. developing a long term incubation study to investigate the feasibility of this remediation method under conditions that are closer to those in-situ;
3. elucidating reaction kinetics by studying oxidized iron precipitation products in a dechlorinated system including mineralogy and surface precipitation; and
4. providing a preliminary assessment of the economics of the in-situ remediation method.

The tasks set by the research team for this initial review period were as follows:

1. develop an experimental design and quality assurance plan for the two-year research project;
2. gather scientific literature pertaining to PCBs, degradation, zero-valent iron, and analytical procedures;
3. obtain materials and instrumentation for laboratory analyses;
4. run a batch experiment to determine conditions required for dechlorination; and
5. better understand the reaction kinetics of PCB dechlorination by zero-valent-iron.

Progress on Tasks
The experimental design was delineated in the project proposal presented by Dr. Gardner in March, 2001. Up to this point, advancements are following the recommended schedule. The graduate student working on this project, Deana Aulisio, has completed a course in environmental sampling and analysis, which includes quality control methods for laboratory procedures, and the 40 hour Occupational Health and Safety (OSHA) training. To ensure the validity of the experimentation, a contract has been established with Northeast Analytical Laboratory in Schenectady, NY to test duplicate samples using state of the art technologies for the measurement of PCBs in sediments.

Sediments were obtained from the New Bedford Harbor Superfund site and the Housatonic River in Pittsfield, MA on November 30, 2001. At this point, the first batch experiment was started. During the experiment two iron ratios (30:1 and 12:1, dry sediment: dry iron) were added to both a highly contaminated marine sediment (New Bedford, MA) and a lesser contaminated freshwater sediment (Pittsfield, MA). Controls for all batch samples are used for quality control. Samples were collected over a two-week period. Extractions were performed using the EPA's SW-846 Method 3550B Ultrasonic Extraction and Northeast Analytical's Standard Operating Procedure for the extraction and cleanup of soil, sediment, and solid samples for PCB analysis. Samples are concentrated to 1 mL in hexane using a Turbovap evaporator with nitrogen gas. A surrogate of congener 207 is added before the extraction to quantify percent recoveries. Clean-up steps include a sulfuric acid wash to remove hydrocarbons and other organic compounds and elemental sulfur, which can interfere with PCB analysis, clean-up.

In order to increase turn around time and maintain control of samples, it was decided to analyze PCB sediment experiments in-house. This required obtaining and setting up a pre-owned gas chromatograph (HP 5890 Series II), done by Jeannie Spear, a research scientist in the Environmental Research Group. A new electron capture detector (ECD) was purchased for the instrument in November, 2001. Other materials needed for the operation of the instrument were obtained over the course of November and December. The instrument was overhauled and set-up by an engineer from the manufacturer in January 2002. This visit included installation of the detector and restoring the GC to working order. After this visit, sample analysis of the sample extracts began immediately.

Based on our desire to quantify for PCB congener concentration rather than just total PCB concentration, the instrumentation we had available, and the recommendation of NEA, the following method was selected for GC analysis of our samples: Standard Operating Procedures for the Gas Chromatographic Analysis of Hydrophobic Organic Contaminant Extracts from Great Lakes Water Samples, USEPA, Great Lakes National Program Office, GLNPO Organics SOP-10. Data accumulation and data analysis are performed using the GC software Chem Station.

Attempts were also made to study the reaction kinetics of ZVI oxidation in water with and without sediment present. Examination was attempted with both X-ray powder diffraction (XRPD), on the reacted Fe surface, performed by Jeannie Spear, and inductively coupled plasma (ICP) on the sample solution at UNH. The results indicate that ZVI remains in samples that are incubated for up to 14 days, although a quantitative analysis has not yet been conducted. Further testing was postponed in order to begin the batch slurry phase of the project. Examination of ZVI oxidation in water will be reexamined in the next reporting period Î samples of sediment are being collected and preserved during the batch experiments to correlate observed dechlorination kinetics with the mass of iron remaining in the zero valence state.

Difficulties Encountered
The major concern at this time is that more dechlorination is occurring after sampling the batch reactors. Samples are stored at 4C to prevent any microbial degradation, but it is unknown whether chemical degradation continues to occur in the sample bottle. To correct this problem, samples will be dried immediately after being removed from the batch reactor and frozen until extraction can take place. Currently samples are being split for preservation or immediate extraction to ensure that the preservation methods are robust and that no additional degradation occurs during storage.

At one point during laboratory analysis, the freeze dryer was malfunctioning. This caused oxidation of the ZVI prepared for the batch reactions. Because of this technical problem, a lot of the ZVI was lost and the ratios of sediment to iron had to be increased. It was expected to run the first batch experiment at a 4:1 and 10:1 ratio, but this was not possible. The freeze dryer has now been repaired by Jeannie Spear. However, it should also be noted that positive results were obtained with higher ratios (less iron in the sediment).

Difficulties were encountered in the iron corrosion experiments. They included determining a way to degas the system (iron corrosion releases hydrogen gas), and finding a way to measure both iron products in solution and those that precipitated.

Anticipated Success in Meeting Project Objectives in Scheduled Project Period
It is anticipated that all objectives will be met in the scheduled two year project period.

Preliminary Results
An iron corrosion experiment was performed with uncontaminated sediment and zero- valent-iron for 28 days. Colloidal ZVI is prepared in the laboratory using 1M FeCl3 and 1.6M NaBH4. It was added at a 1:4 ratio to the sediment in test tubes filled with 10-2 M NaCl. Solid samples were taken at different time periods and viewed using x-ray powder diffraction (XRPD) at the University of New Hampshire by Jeannie Spear in December of 2001. Results show (Figure 1) that FeOH compounds precipitated and the amount of ZVI decreased over time. There was still ZVI remaining in the system after 28 days. However, these samples were not contaminated with PCBs. This experiment will be repeated with contaminated sediments during the next batch experiment.

All samples from the first batch experiment have been analyzed on the GC-ECD. Quantification of congener concentrations is still underway. A calibration curve of Aroclor standards was established over a range of 0.0165 ug/mL to 16.45 ug/mL in order to encompass both the high and low contaminated samples. Internal standards of congeners 30 and 204 are used for calculation of concentrations using response factors and area counts of congener peaks.

The batch experiment provided good results. It showed that dechlorination was occurring at low iron to sediment ratios for both the highly contaminated marine sediment (Figure 2) and the less contaminated river sediment (Figure 3). Percent removals are shown for samples taken at 14 days: the average for both cases were approximately 45% removal.

Tasks and activities for next reporting period

Tasks for the next reporting period
Instrumentation related tasks for the next reporting period include:

1. mastering the Chem Station data analysis program to maximize the automation of congener concentration quantification. This should decrease the time required for data analysis and ensure more uniform treatment of data;
2. determining the detection limits of the instrument using calibration standards;
3. obtaining a pre-owned auto-analyzer for the GC in order to run samples for 24 hour periods to increase data output and production time.

Experimental related tasks for the next reporting period include:

1. comparing and refining in-house analyses and results based on results of a contracted laboratory, Northeast Analytical;
2. characterization of the oxidation rates and complexations of ZVI in water and in a contaminated sediment;
3. setting up more batch experiments to determine kinetics, amount of iron, and type of iron; and
4. developing standard operating procedures for complete analysis of contaminated sediment from the sampling of the batch experiments to the quantification of the gas chromatographic data.

Work plan to accomplish tasks
The work plan is predicted to proceed according to the project proposal. We will continue to develop and refine our laboratory procedures in order to optimize sample analysis and data accumulation. Now that the GC is set up and working properly, batch experiments can be sampled and analyzed in a shorter time frame, which will speed up the process and increase our knowledge on the processes involved in dechlorinating PCBs.

Concerns or difficulties
At this time, no concerns or difficulties are expected to obstruct further analyses in this project.

Expenditures
Expenditures are in the range anticipated for the work accomplished to date.